(i) Field of the Invention
The invention relates broadly to woven fabric that is relatively stiff in one direction and relatively flexible in the other. More particularly, it relates to coilable belting fabrics that may be used in seat belt safety harnesses and have reduced tendency to twist and jam in belt retractor mechanisms and associated reversal hardware.
(ii) Prior Art
Safety seat belt harnesses have been used for many years to restrain passengers in vehicles involved in collisions or rapid deceleration. Most such harnesses include a lap belt. On most automobiles to-day, one part of the lap belt is coupled to a self-retracting mechanism which coils part of the belt out of sight and out of sunlight when not in use. Self-retracting mechanisms to-date have not been completely effective, since belts which have a tendency to twist (or fold or rope) can result in the retractor jamming. Jamming of the belt in the retractor can make it impossible for a person to use the seat belt. Also, it can damage the belt and the use of any twisted belt in a harness can result in higher local pressures being applied to part of a person involved in a collision or rapid deceleration.
Various attempts have been made to overcome the foregoing problems.
U.S. Pat. No. 3,606,914 relates to a seat belt with reduced tendency to roll up laterally. It discloses a woven seat belt fabric in which the weft (or filling) threads consist of monofilaments of synthetic linear material, preferably monofilaments of polyethylene glycol terephthalate {or poly(ethylene terephthalate)}, with the monofilaments preferably having a diameter within the range of from 0.15 mm to 0.4 mm. Such a seat belt has stiffer filling yarns than warp yarns. The patent is silent concerning the conversion efficiency of breaking load from the individual warp yarns to fabric along the warp yarns.
U.S. Pat. No. 3,321,245 discloses a self-retracting seat belt in which the warp yarns include eccentrically positioned pretensioned elastic yarns to promote coiling of the belt in spiral form without twisting. It does not involve filling yarns that are stiffer than the warp yarns.
Various U.S. Patents relate to woven fabrics in which the fabric is relatively stiff in the filling direction and relatively flexible in the warp direction.
U.S. Pat. Nos. 3,173,185 and 3,474,885 disclose a woven fabric having materially greater stiffness in one direction than the other. Such stiffness is obtained by chemically fusing the yarns in the desired direction. Specifically, the filling yarns are formed of viscose rayon which may be fused after weaving by treatment with a zinc chloride solution, while the warp yarns are formed of cotton which is not fused by zinc chloride solution.
U.S. Pat. No. 4,107,371 discloses an open weave fabric which is relatively stiff in the filling direction and relatively flexible in the warp direction. The filling yarns are made of heavy denier monofilaments which are relatively stiff. The warp yarns are made of a multifilament core, such as polyester yarn, which is coated with a thermoplastic polymer, such as plasticized polyvinyl chloride. After weaving, the fabric is subjected to a heat treatment which causes the thermoplastic coating to flow, thereby interlocking and stabilizing the fabric.
Various U.S. Patents relate to the application of uniform coatings of resin to pre-existing woven fabrics in order to improve the fabric properties in both warp and weft directions.
U.S. Pat. No. 3,624,016 is directed towards the concept of using polyurethanes as textile assistants in order to enhance the abrasion resistance, crease recovery, softness, and other properties of fabrics, including polyester fabrics.
U.S. Pat. No. 2,639,852 discloses a seat belt of cotton webbing which in impregnated after weaving with a flexible thermoplastic material, such as a vinyl or acrylic resin.
U.S. Pat. No. 4,002,791 is directed towards a belt which is uniformly coated with a polyurethane composition, which belt may be a polyester fabric.
Multifilament yarns are conventionally treated with lubricants, sizes and adhesives in order to facilitate subsequent processing.
U.S. Pat. No. 3,296,062 discloses the use of a nylon filling (weft) yarn treated with resorcinol formaldehyde latex in a woven fabric in which the filling yarn is predominantly visible at the fabric's surface. The disclosure is particularly directed to fabrics which are subsequently coated, and to reducing the weight and stiffness caused by the reinforcing fabric in such composite structures. While the patent refers to automotive seat belts at column i, line ii, no specific examples are given thereto.